San Francisco, Calif., Mar 24, 2010 / 01:09 am (CNA).- Although the same actions have been required of their adversaries, opponents of Proposition 8 have objected to a federal judge’s ruling that they must turn over internal campaign materials to the lawyers of Prop. 8 supporters.

The successful California ballot measure which restored the definition of marriage is being challenged in court. The challenge is the first federal case examining whether reigning interpretations of the U.S. Constitution bar states from outlawing same-sex “marriages.”

On Monday U.S. District Chief Judge Vaughn Walker said sponsors of Prop. 8 were entitled to the information as evidence in their defense against the challenge to the ballot measure, the Associated Press reports.

The American Civil Liberties Union (ACLU) and Equality California, two of the groups affected by the decision, said they are reviewing the judge’s order to determine whether to appeal it. They had argued that the campaign materials were irrelevant and said it was unfair to burden them with the expense of searching through tens of thousands of old e-mails.

Geoffrey Kors, Equality California's executive director, said they believe the decision is incorrect.

"A core issue in the case is whether the motivation of those who put Prop. 8 on the ballot is animus. Why people opposed Prop. 8 is not relevant," he said, according to the Associated Press.

Protect Marriage, a sponsor of Prop. 8, has already been required to hand over similar materials to lawyers representing the plaintiffs in the case.

Judge Walker said Magistrate Joseph Spero had taken substantial steps to make the Prop. 8 opponents’ task easier. He said they failed to substantiate their argument that the magistrate’s order imposes an “undue burden.”

An appointee of President George H.W. Bush, Judge Walker is himself homosexual, the San Francisco Chronicle has reported.

The proceedings in the trial of Prop. 8 have been on hiatus because Judge Walker wanted to review the evidence before scheduling closing arguments.

On Monday he gave Protect Marriage’s lawyers until April 12 to submit their remaining evidence.